Cathode ray tube having multisegment target extending through envelope wall



July 15, 1969 w. c. DAVIS CATHODE RAY TUBE HAVING MULTISEGMENT TARGET EXTENDING THROUGH ENVELOPE WALL Filed Oct. :5, 1967 FIG 1 INVENTOR WARREN 6. DAVIS A EN United States Patent 3,456,145 CATHODE RAY TUBE HAVING MULTISEGMENT TARGET EXTENDING THROUGH ENVELOPE WALL Warren C. Davis, 'Cohasset, Mass., assignor to Raytheon Company, Lexington, Mass., a corporation of Delaware Filed Oct. 3, 1967, Ser. No. 672,497 Int. Cl. H01j 31/02 US. Cl. 313--73 1 Claim ABSTRACT OF THE DISCLOSURE Background of the invention This invention relates to cathode ray tubes suitable for use in electronic systems for receiving an electrical signal indicative of the particular location of a detected item and operative in response to such signal to transmit such location information to suitable processing apparatus such as a computer, for example. Such tubes are also usable in other types of equipment such as machine control apparatus and counting devices. The tube is provided with a scanning electron beam which, in response to the incoming signal, is made to scan a selected portion or portions of a multisegment target, each segment of which is separately interconnected into external circuitry leading to or forming a part of the processing apparatus.

First attempts to make multisegment targets suitable for such tubes embodied the fabrication of glass substrates coated in selected areas with a conductive silver paste. Terminal pins extended through the walls of the tube envelope adjacent the target and were connected to respective conductive areas by metal tabs which engaged spring-loaded eyelets carried by the target areas. This structure embodied many parts and connections which affected reliability and signal uniformity from segment to segment.

In later developments of this tube structure, the silver paste target areas were replaced by preformed thin metal plates mounted individually in spaced relation to one another on a dielectric substrate and making simpler electrical connections to the plates. This structure had improved reliability, uniformity, and signal output quality. However, here again, the target involved the fabrication and handling of many small parts, resulting in relatively high cost.

The present invention overcomes many of the disadvantages and undesirable features of the prior art by the provision of a novel self-supporting target which is fabricated by simple, well-known techniques and which is sealed in a novel sandwich fashion to a glass envelope so as to provide its own terminals, thus eliminating the requirement for a separate terminating header or stem. Welding of target elements to header terminals is eliminated, improving reliability and reducing labor costs.

Summary of the invention The target of the present invention comprises a single disc of selected metal which is fabricated by stamping,

photoetching, engraving, electrical-discharge machining, or other known shaping technique as an initial one-piece thin metal structure having preformed segments joined together only by a continuous peripheral rim. The target disc is of a diameter larger than the outside diameter of the tube envelope and is adapted to be sandwiched in spanning relation to the interior of the envelope beneath the faceplate or end seal portion thereof, with the outer ends of the segments projecting radially outwardly from the envelope. After the target is sealed in place, the peripheral rim is simply fractured or punctured so as to electrically isolate the individual segments, the outwardly projecting portions of the segments thus providing simple and readily accessible means whereby external circuitry may be connected to the target.

Brief description of the drawings FIG. 1 is a side elevational View of a cathode ray tube embodying the invention;

FIG. 2 is an enlarged axial sectional view of the target end portion of the tube of FIG. 1 showing the parts in exploded relation;

FIG. 3 is an enlarged elevational view of the target before assembly with the tube envelope;

FIG. 4 is a view similar to FIG. 3 showing the target as it appears after assembly with the envelope and showing the adjacent portion of the envelope in section; and

FIG. 5 is an enlarged fragmentary view of a portion of the target illustrating a modification thereof.

Description of the preferred embodiments Referring more particularly to the drawings wherein like characters of reference designate like parts through out the several views, there is shown in FIG. 1 a cathode ray tube 10 embodying a preferred form of the invention. Tube 10 includes a hollow glass envelope 12 Within one end of which is a conventional electron gun 14 which generates a beam or stream of electrons in the usual and well-known manner of cathode ray tubes. The adjacent end of the envelope comprises a solid dielectric base 16 which supports the gun 14 and which carries outwardly extending terminal pins 18 to which individual component parts of the gun are connected by leads 20 and whereby the tube may be inserted into suitable electrical equipment designed to provide such component parts I with selected potentials, as is well known. Included among such parts are deflection plates 22 upon which an incoming signal is impressed to cause the electron beam generated by the gun 14 to scan selected areas of a target 24 in accordance with information which is contained in the incoming signal. The signal is transmitted to plates 22 through one or more terminal pins 18 and leads 20, as is well known in tubes of this character. Other means may be employed for deflecting the electron beam, such as an external deflection yoke, if desired.

The target 24 is initially formed from a disc of selected metal which can be relatively easily sealed to the glass from which the envelope is made to form a vacuum tight seal, such as Kovar or chrome alloy, and is coated with a material having a good secondary emission ratio such as a film of aluminum or magnesium which may be, for example 1000 A. thick. The disc is mounted in the tube envelope at a point remote from the gun 14 and in position to be scanned by the electron beam. In FIG. 1 the target 24 is located adjacent the end of the envelope opposite the gun 14 and extends transversely of the envelope so as to span the interior thereof.

Target disc 24 is of a diameter greater than the outside diameter of the envelope so that a marginal portion thereof projects beyond the envelope wall in all directions, as shown, the envelope being open-ended where the target is located so that an annular end 28 (FIG. 2) thereof abuts one side of the target 24. The envelope is sealed, however, by a glass end cap 26 having an annular end surface 30 which abuts the opposite side of target 24 and has a diameter of the opposing adjacent end 28 of the envelope. Thus, there is formed a vacuum-tight seal when the glass end surfaces 2830 are sealed to the opposite sides of the metal target 24. The target 24 is provided with a selected number of segments 32a, 321;, etc., as shown in FIG. 3, the entire portion of each segment being completely separated from adjacent segments by slots 34 except at their outer ends where they are joined initially by a marginal or peripheral portion 36 of the target disc 24. The separations between segments are provided by any suitable technique whereby the separations will be as narrow as possible but still effectively electrically isolate the separated portions of the segments from one another. For example, the separations or slots 36 in disc 24 may be photoetched, engraved, electrical discharge machined, stamped, or otherwise formed by known techniques. Where stamping techniques are employed, one edge 38 of each segment may be bent rearwardly so as to extend in a direction away from the electron gun. Such modification is clearly shown in FIG. wherein it will be seen that the slots 34 are formed by striking out flanges 38 which thus are separate from adjacent segments but still partially fill the slots so as to considerably limit the size of the openings through which the electron beam can pass.

The outer ends of the radial slots 34 have enlarged openings 40 (FIGS. 2 and 3) which may be circular or elongated in shape and through which glass from the opposed end surfaces 28-30 may flow to form direct glass-to-glass seals when the thin target is being assembled with an envelope and end cap. This has been found to provide an appreciably stronger seal than is achieved by a thin metalto-glass seal alone.

After a target of the above character has been sealed in a cathode ray tube as described above, the marginal or peripheral portion 36 thereof is ruptured or punctured adjacent the openings 40. This is clearly shown in FIG. 4 wherein such punctures are indicated by numeral 42. The punctures 42 thus completely separate the segments from one another. Furthermore, the portion of each segment which extends radially outwardly of the envelope provides a terminal means to which circuitry may be readily and easily connected without the requirement for additional headers or terminals.

The metal target is thick, being preferably about .020 inch, and is stiff enough to be entirely free floating and self-supporting within the envelope, thus eliminating the need for a separate supporting structure.

In the operation of a tube of this character, the electron beam gun 14 is caused by the deflection plates 22, under the influence of an input signal, to scan the adjacent side of the target 24 and specifically the segments 32 thereof. Impingement of the electron beam upon the particular seg- 4 ments causes secondary emission of electrons which are collected by a suitable collecting means such as an Aquadag coating 50 on the inner surface of the adjacent portion of the enevelope and maintained at a required potential for this purpose. This creates current flow in the segment circuit, which current passes outwardly from the major portion of each segment through its external terminal portion into the processing apparatus.

From the foregoing, it will be apparent that all of the objectives of this invention have been achieved by the novel cathode ray tube described hereinbefore. It will be apparent, however, that various modifications and changes may be made by those skilled in the art without departing from the spirit of the invention as expressed in the accompanying claim.

I claim:

.1. A metal disc target for a cathode ray tube including a dielectric envelope having a cylindrical target-supporting portion, said target being mounted in said portion of the envelope opposite an electron gun which generates a scanning electron beam, said target spanning the interior of said portion of the envelope and located in the path of said electron beam and comprising a planar array of pieshaped segments disposed in a common plane and electrically separated from one another, each segment having an integral portion thereof supported in and extending through the wall of the envelope and projecting outwardly therefrom as a terminal therefor, said segments being electrically separated from each other by radial slots of a length to extend through said envelope and enlarged in the areas where contacted by section of said envelope, said envelope sections being fused to one another within said enlarged areas of the slots, with one side edge of each segment adjacent a slot being provided with an angled flange extending longitudinally within the adjacent slot to intercept the electron beam entering said slot during a scanning cycle whereby the scanning electron beam will always be prevented from passing through a slot.

References Cited UNITED STATES PATENTS ROBERT SEGAL, Primary Examiner US. Cl. X.R. 

